The presence of genetic alterations in the tyrosine kinase domain of the oncogene (eg. EGFR and ALK) is associated with the clinical response to tyrosine kinase inhibitors (TKIs) in patients with non-small cell lung cancers. Therefore, the detection of altered genetic alterations is useful for predicting the treatment response for TKIs in non-small cell lung cancer patients. However, good quality tumor tissues are available only in <50% of patients with inoperable lung cancer for mutation analysis. In this study, the investigators will detect and quantify the genetic alterations in plasma. the investigators will investigate if the serial measurement of cancer-derived genetic alterations in plasma can provide a means for monitoring disease progression, as well as treatment response. In addition the investigators will analysis the resistant mechanism of TKIs and chemotherapy with plasma tumor DNA.